Communication method and related product

ABSTRACT

A communication method and a related product, in which the method is implemented on an access network side and includes: an access network device sending indication information to user equipment, where the indication information is used to indicate a manner of receiving multicast service data, and the receiving manner includes a unicast manner and/or a multicast manner; and the access network device sending the multicast service data in the unicast manner and/or the multicast manner indicated by the indication information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2018/124928, filed on Dec. 28, 2018, which claims priority toChinese Patent Application No. 201711453932.1, filed on Dec. 28, 2017.The disclosures of the aforementioned applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

Aspects of the present invention relate to the field of communicationstechnologies, and in particular, to a communication method and a relatedproduct.

BACKGROUND

Multicast is a manner in which a plurality of receive ends form amulticast group and a data source transfers data to the plurality ofreceive ends in the multicast group. With rapid development of mobilecommunications services, a large quantity of multimedia services emerge.For some application services such as video live broadcast, televisionbroadcast, a video conference, online education, and an interactivegame, a plurality of receive ends can simultaneously receive same data.Compared with common data, these mobile multimedia services arecharacterized by a large data volume, long duration, and latencysensitivity.

To make the most effective use of mobile network resources, a multimediabroadcast/multicast service (MBMS) is introduced into the ThirdGeneration Partnership Project (3GPP) Rel-6, to provide a multicastservice for a universal mobile telecommunications system (UMTS) by usinga cellular network. Standardization of the MBMS is always in anevolution process.

To ensure that the MBMS can cover a sufficient area and that all userequipments (User Equipment, UE) in a multicast group can successfullyreceive multicast service data, an MBMS system sets a correspondingmodulation and coding scheme and a multimedia resource by using userequipment with the worst signal quality in the multicast group as areference. Because attenuation of wireless signal strength and adistance have an exponential relationship, spectral efficiency of userequipment with relatively poor signal quality in the multicast group isusually five to dozens of times less than average spectral efficiency,resulting in very low transmission efficiency.

SUMMARY

A technical problem to be resolved in embodiments of the presentinvention is low transmission efficiency of multicast communication. Acommunication method and a related product are provided, to improve thetransmission efficiency of the multicast communication.

According to a first aspect, an embodiment of the present inventionprovides a communication method, including:

sending, by an access network device, indication information to userequipment, where the indication information is used to indicate a mannerof receiving multicast service data, and the receiving manner includes aunicast manner and/or a multicast manner; and

sending, by the access network device, the multicast service data in theunicast manner and/or the multicast manner indicated by the indicationinformation.

The access network device may be a base station or another device thatprovides a network access function to the user equipment. Each of theunicast manner and the multicast manner corresponds to a datatransmission manner. Using data sending as an example, in the unicastmanner, a transmit end and a receive end of data are in a one-to-onecorrespondence. In this manner, the receive end and the transmit end maybe well matched based on respective data transmission capabilities, andretransmission is facilitated. In the multicast manner, a transmit endand receive ends of data are in a one-to-many correspondence. In thismanner, the transmit end sends same data to the plurality of receiveends on one air interface resource, thereby saving air interfaceresources. It may be understood that a data receiving manner correspondsto a data sending manner. For example, if a transmit end sends data inthe unicast manner, a receive end receives the data in the unicastmanner.

The indication information may be explicit indication information, forexample, a dedicated flag bit. Alternatively, the indication informationmay be an implicit indication manner, for example, sending correspondingconfiguration information. More specifically, for example, assuming thatit is required to instruct to receive the service data in the multicastmanner, only configuration information of a multicast service may besent.

In addition, before the user equipment receives the multicast servicedata in the unicast manner and/or the multicast manner, a radio bearerneeds to be established, and corresponding configuration information isrequired for establishing the radio bearer. To distinguish betweenconfiguration information used for radio bearers corresponding to twomanners of receiving the multicast service data, the configurationinformation used for the radio bearer corresponding to the unicastmanner for receiving the multicast service data may be referred to asunicast configuration information, and the configuration informationused for the radio bearer corresponding to the multicast manner forreceiving the multicast service data may be referred to as multicastconfiguration information.

In this embodiment of the present invention, sending of the multicastservice data is not limited to that all user equipments that receive themulticast service data receive the multicast service data in themulticast manner, thereby facilitating exclusion of user equipment thataffects transmission efficiency, and improving the transmissionefficiency of the multicast service.

In an optional implementation, that the access network device providesthe configuration information about how to receive the multicast servicedata is further provided. The method further includes:

sending, by the access network device, the configuration information tothe user equipment, where the configuration information is used toreceive the multicast service data.

The configuration information is described above. The configurationinformation may be classified into the multicast configurationinformation and the unicast configuration information, which arerespectively used to establish the radio bearer applicable totransmitting the multicast service data in the multicast manner, andestablish the radio bearer applicable to transmitting the multicastservice data in the unicast manner. In this embodiment of the presentinvention, the configuration information and the indication informationmay be sent by using same signaling. If the configuration information isused as implicit indication information, the configuration informationmay be used as the indication information.

In this embodiment, the configuration information is used to receive themulticast service data, because the multicast service data may bereceived in the unicast manner and/or the multicast manner, theconfiguration information may include the multicast configurationinformation and the unicast configuration information, or include onlyconfiguration information corresponding to the manner of receiving themulticast service data.

In an optional implementation, specific content of the configurationinformation is further provided. The configuration information includes:

at least one of configuration information of a multicast bearer,multicast session information corresponding to the multicast bearer,logical channel information of the multicast bearer, multicastscheduling identifier information, information about a transmissionchannel for sending the multicast service data in the multicast manner,information about a transmission channel for sending the multicastservice data in the unicast manner, multicast logical channelinformation, measurement configuration information of the transmissionchannel of the multicast service data, and multicast-associated unicastconfiguration information.

The configuration information is information mainly used to establish aradio bearer. The foregoing information is used as an example of apossible implementation, and should not be understood as a uniquelimitation on this embodiment of the present invention.

In an optional implementation, a specific solution in which the accessnetwork device obtains multicast service information is furtherprovided. The method further includes:

receiving, by the access network device, the multicast serviceinformation sent by the user equipment or a core network device, wherethe multicast service information is used to instruct the user equipmentto receive the multicast service data, and the multicast serviceinformation includes identifier information of the user equipment andidentifier information of the multicast service.

The access network device needs to indicate a manner used by the userequipment to receive the multicast service data, so that the accessnetwork device needs to learn of the user equipment that participates inreceiving the multicast service data and a change status of the userequipment. Therefore, this solution is provided in this embodiment. Theforegoing multicast service information may be sent after a multicastsession is established, or may be update information sent by the corenetwork device after user equipment joins or leaves a multicast group.The user equipment may report the multicast service information at anytime, for example, after it is determined that the user equipmentsuccessfully joins the multicast session, or after the manner ofreceiving the multicast service is switched.

In an optional implementation, an optional implementation in which theaccess network device obtains the multicast service information isfurther provided. The receiving, by the access network device, themulticast service information sent by the user equipment or a corenetwork device includes:

receiving, by the access network device, a multicast sessionestablishment request sent by the core network device, where themulticast session establishment request includes the identifierinformation of the user equipment and the identifier information of themulticast service; or

receiving, by the access network device, multicast member changeinformation sent by the core network device or the user equipment.

This embodiment provides a specific implementation solution of obtainingthe multicast service information from the user equipment and obtainingthe multicast service information from the core network device. Themulticast session establishment request is a request used by the userequipment to request to establish a multicast session. The accessnetwork device may obtain the multicast service information by using therequest without increasing signaling. In addition, the access networkdevice may obtain the multicast service information in another case,which is described above and is not described herein again.

The multicast member change information is information sent when userequipment in the multicast group changes. The information may includethe identifier information of the multicast service and identifiers ofall user equipments in the multicast group. Alternatively, only changedinformation may be sent, for example, an identifier of user equipmentand a change identifier, and the change identifier is used to indicatewhether the user equipment newly joins the multicast group or leaves themulticast group.

In an optional implementation, an implementation in which the accessnetwork device obtains the multicast service data is further provided.The method further includes:

instructing, by the access network device based on a quantity of userequipments that receive the multicast service data, the user equipmentto receive the multicast service data in the unicast manner and/or themulticast manner; or

receiving, by the access network device, channel measurement informationsent by the user equipment, and instructing, based on the channelmeasurement information, the user equipment to receive the multicastservice data in the unicast manner and/or the multicast manner.

In this embodiment, the former manner of receiving the multicast servicedata is related to the quantity of user equipments that receive themulticast service data, and the access network device may use athreshold as a comparison standard. Specifically, if the quantity ofuser equipments that receive the multicast service data is greater thanthe threshold, the multicast manner is used; or if the quantity of userequipments that receive the multicast service data is less than thethreshold, the unicast manner is used. In this embodiment, it is mainlyconsidered that the more user equipments that receive the multicastservice data, the more air interface resources are saved if themulticast manner is used. The threshold may be configured in the accessnetwork device, or may be specified by the core network device oranother device that manages the access network device. This is notuniquely limited in this embodiment of the present invention.

The latter manner of receiving the multicast service data is related tochannel quality of the user equipment, and specific related content maymainly include the following several types.

A. An absolute value of the channel quality is used. To be specific, ifthe channel quality is lower than a particular threshold, the unicastmanner is used; otherwise, the multicast manner is used. In thisembodiment, it is mainly considered that the poorer the channel qualityis, the more likely overall transmission efficiency of the multicastservice is reduced. Therefore, it may be considered to use the unicastmanner to send the multicast service data to the user equipment.

B. A relative value of the channel quality is used. For example, in amulticast group, if a difference between channel quality of userequipments is relatively large, user equipments with relatively poorchannel quality reduce transmission efficiency of a multicast service.Therefore, the user equipments with the relatively poor channel qualitymay be removed from the multicast group. If there are a relatively largequantity of user equipments with relatively poor channel quality, theuser equipments may further form another multicast group.

C. Grouping is performed based on parameters that affect the channelquality. For example, some parameters affect the channel quality, forexample, distribution of user equipments, a movement speed of the userequipment, and a movement direction of the user equipment. Based onthis, the user equipments may be grouped. If a quantity of userequipments in the group is sufficient, the user equipments form amulticast group. Otherwise, the multicast service data is received inthe unicast manner.

In this embodiment, the channel measurement information may be channelmeasurement feedback information, or may be any other information thatcan reflect the channel quality. The user equipment may periodicallyfeed back the channel measurement information, or may feed back thechannel measurement information when a particular condition issatisfied. The particular condition may be that the channel quality orthe parameter that affects the channel quality changes, or may be that acondition in which the receiving manner needs to be switched issatisfied. In this embodiment of the present invention, when and howsending of the channel measurement information to the access networkdevice is triggered is not limited.

In an optional implementation, an implementation solution in which themulticast group is further divided is further provided. Theconfiguration information includes first multicast configurationinformation and second multicast configuration information; and

the indication information indicates that the manner of receiving themulticast service data includes the multicast manner, and the indicationinformation indicates that the first multicast configuration informationor the second multicast configuration information is used to receive themulticast service data.

In this embodiment, the multicast configuration information includes atleast two pieces of multicast configuration information. In this way,the user equipments that receive the multicast service data may bedivided into two sub-multicast groups. Because the two sub-multicastgroups use different multicast configuration information, differentradio bearers are established, and transmission efficiency in thedifferent sub-multicast groups may be maximized.

In an optional implementation, an implementation solution in which themulticast group is further divided is further provided. If the receivingmanner includes the multicast manner, the indication information furtherincludes: indicating that the multicast service data is received in afirst multicast manner or a second multicast manner.

A difference between this embodiment and the previous embodiment lies inthat the access network device may send only one piece of multicastconfiguration information to the user equipment. For the indicationinformation, refer to the foregoing descriptions in which the indicationinformation may be implicit or explicit, and details are not describedherein again.

In an optional implementation, a solution of accelerating transmissionof the multicast service data is further provided. The method furtherincludes:

sending, by the access network device, at least one data packet in themulticast service data in the unicast manner as instructed by the userequipment; or

sending, by the access network device, at least one data packet in themulticast service data in the unicast manner as indicated by the corenetwork device; or

sending, by the access network device, at least one data packet in themulticast service data in the unicast manner based on type informationof the at least one data packet.

In this embodiment, in the first implementation, the user equipmentspecifies that the multicast service data needs to be sent in theunicast manner. In the second implementation, the core network devicespecifies that the multicast service data needs to be sent in theunicast manner. In the third implementation, the access network devicedetermines that the multicast service data needs to be sent in theunicast manner. The specifying manner may be adding correspondingidentifier information to the data packet in the multicast service data,and the identifier information may be specifying that the data packetneeds to be sent in the unicast manner. Alternatively, the specifyingmanner may be specifying that a data packet of a particular type ofmulticast service data needs to be sent in the unicast manner. Forexample, it is specified that data between the latest I frame that hasbeen sent in the multicast manner and a data frame that is being sent inthe multicast manner needs to be sent in the unicast manner.Alternatively, it is specified that a single data packet of multicastservice data needs to be sent in the unicast manner. In the foregoingtwo examples, the data in the former example may be attributed to datarequired for starting a service corresponding to the multicast service,so that the user equipment can start the service corresponding to themulticast service as soon as possible, for example, start video playing.The latter example may correspond to various application scenarios suchas data retransmission and timely transmission of important data.

In an optional implementation, an implementation solution in which themulticast service data is sent at a protocol layer in the multicastmanner and/or the unicast manner is further provided. The at least onedata packet is multicast service data that has been sent in themulticast manner and that is buffered in the access network device, ormulticast service data that has been sent in the multicast manner andthat is received from a multicast service data source.

In this embodiment, the multicast service data sent in the unicastmanner may be retransmitted. Therefore, a segment of data may bebuffered first, and it was waiting for whether there is a retransmissionrequest feedback. If there is no retransmission request feedback, thedata may be deleted. Therefore, the buffered multicast service dataherein may be multicast service data within a period of time, andmulticast service data that is sent a long time ago may be deleted.

After the multicast service data sent in the unicast manner iscompletely sent, the multicast manner may be switched to for sending theservice data, or the unicast radio bearer may be kept waiting for newmulticast service data that needs to be sent in the unicast manner, ornotification information may be sent to a receiver to notify that themulticast service data sent in the unicast manner is completely sent. Aspecific notification manner may be an explicit notification manner. Forexample, an end indication is added to the last data packet.Alternatively, a specific notification manner may be an implicitnotification manner. For example, the multicast configurationinformation is sent. Content executed after the multicast service datasent in the unicast manner is completely sent is not uniquely describedin this embodiment of the present invention.

In an optional implementation, a multicast service retransmission methodis further provided. The method further includes:

receiving, by the access network device, receiving status informationsent by the user equipment, where the receiving status information isused to indicate a receiving status of the data packet in the multicastservice data; and

sending, by the access network device, an unsuccessfully received datapacket in the multicast service data to the user equipment in theunicast manner based on the receiving status information.

In this embodiment, the receiving status information is information usedto indicate the receiving status of the data packet, and the accessnetwork device is enabled to learn of the data packet that needs to beretransmitted to the user equipment. Therefore, the receiving statusinformation has various representation forms. For example: 1. a sequencenumber of the data packet that needs to be retransmitted is directlynotified; and 2. feedback information is sent, where the feedbackinformation includes information about whether all data packets havebeen received. The foregoing two possible examples should not beunderstood as a uniqueness limitation on this embodiment of the presentinvention. A specific manner used to notify the access network device ofdata packets that need to be retransmitted is not uniquely limited inthis embodiment of the present invention.

In an optional implementation, a solution in which the protocol layersupports sending of the multicast service data in the unicast manner isfurther provided. The method further includes:

sending, by the access network device, to-be-sent multicast service datato a unicast radio link control (RLC) entity by using a packet dataconvergence protocol (PDCP) layer, and sending the to-be-sent multicastservice data in the unicast manner.

A solution of sending the multicast service data in the multicast manneris not limited in this embodiment of the present invention. In thisembodiment, the multicast service data is allocated to the unicast RLCat the PDCP layer, so that the multicast service data is sent in theunicast manner.

In an optional implementation, an implementation solution forfacilitating retransmission is further provided. The method furtherincludes:

replicating, by the access network device, the to-be-sent multicastservice data at the packet data convergence protocol PDCP layer, andstoring the to-be-sent multicast service data.

In this embodiment of the present invention, the to-be-sent multicastservice data may be stored in a buffer, to respond to a possibleretransmission request. Storage space may be set at the PDCP, or may beset at the RLC. This is not limited in this embodiment of the presentinvention.

In an optional implementation, a solution in which the protocol layersupports sending of the multicast service data in the unicast manner isfurther provided. The method further includes:

sending, by the access network device, to-be-sent multicast service datato a multicast radio link control RLC entity by using a multicast packetdata convergence protocol PDCP layer; sending, by the multicast radiolink control RLC entity, the to-be-sent multicast service data to aunicast medium access control (MAC) entity; and sending, by the unicastmedium access control MAC entity, the to-be-sent multicast service datain the unicast manner.

In this embodiment, the RLC entity allocates the multicast service datato the unicast MAC entity, so that the multicast service data is sent inthe unicast manner.

According to a second aspect, an embodiment of the present inventionfurther provides a communication method. This embodiment is implementedon a side (for example, the user equipment) that receives data sent bythe foregoing access network device, and is in a correspondence with theforegoing solution implemented on the side of the access network device.For specific content, refer to the foregoing descriptions, and repeatedparts are not described again in subsequent embodiments. Thecommunication method includes:

receiving, by user equipment, indication information sent by an accessnetwork device, where the indication information is used to indicate amanner of receiving multicast service data, and the receiving mannerincludes a unicast manner and/or a multicast manner; and

receiving, by the user equipment, the multicast service data in theunicast manner and/or the multicast manner indicated by the indicationinformation.

In an optional implementation, the method further includes:

receiving, by the user equipment, configuration information sent by theaccess network device, where the configuration information is used toreceive the multicast service data.

In an optional implementation, the configuration information includes:

at least one of configuration information of a multicast bearer,multicast session information corresponding to the multicast bearer,logical channel information of the multicast bearer, multicastscheduling identifier information, information about a transmissionchannel for sending the multicast service data in the multicast manner,information about a transmission channel for sending the multicastservice data in the unicast manner, multicast logical channelinformation, measurement configuration information of the transmissionchannel of the multicast service data, and multicast-associated unicastconfiguration information.

In an optional implementation, the method further includes:

sending, by the user equipment, multicast service information to theaccess network device, where the multicast service information is usedto instruct the user equipment to receive the multicast service data,and the multicast service information includes identifier information ofthe user equipment and identifier information of a multicast service.

In an optional implementation, the sending, by the user equipment,multicast service information to the access network device includes:

sending, by the user equipment, multicast member change information tothe access network device.

In an optional implementation, the method further includes:

selecting, by the user equipment based on a quantity of user equipmentsthat receive the multicast service data, the unicast manner and/or themulticast manner for receiving the multicast service data; or

selecting, by the user equipment based on channel measurementinformation of the user equipment, the unicast manner and/or themulticast manner for receiving the multicast service data.

In an optional implementation, the configuration information includesfirst multicast configuration information and second multicastconfiguration information; and

the indication information indicates that the manner of receiving themulticast service data includes the multicast manner, and the indicationinformation indicates that the first multicast configuration informationor the second multicast configuration information is used to receive themulticast service data.

In an optional implementation, the method further includes:

instructing, by the user equipment, the access network device to send atleast one data packet in the multicast service data in the unicastmanner.

In an optional implementation, the method further includes:

sending, by the user equipment, receiving status information to theaccess network device, where the receiving status information is used toindicate a receiving status of the data packet in the multicast servicedata; and

receiving, by the user equipment, an unsuccessfully received data packetin the multicast service data sent by the access network device.

In an optional implementation, the method further includes:

performing packet loss detection at a packet data convergence protocolPDCP layer to obtain the receiving status information.

In an optional implementation, the method further includes:

sending, by the user equipment at a unicast radio link control RLCentity, the received multicast service data to the multicast packet dataconvergence protocol PDCP layer.

According to a third aspect, an embodiment of the present inventionfurther provides an access network device, including:

an indication sending unit, configured to send indication information touser equipment, where the indication information is used to indicate amanner of receiving multicast service data, and the receiving mannerincludes a unicast manner and/or a multicast manner; and

a data sending unit, configured to send the multicast service data inthe unicast manner and/or the multicast manner indicated by theindication information.

In an optional implementation, the access network device furtherincludes:

a configuration sending unit, configured to send configurationinformation to the user equipment, where the configuration informationis used to receive the multicast service data.

In an optional implementation, the configuration information includes:

at least one of configuration information of a multicast bearer,multicast session information corresponding to the multicast bearer,logical channel information of the multicast bearer, multicastscheduling identifier information, information about a transmissionchannel for sending the multicast service data in the multicast manner,information about a transmission channel for sending the multicastservice data in the unicast manner, multicast logical channelinformation, measurement configuration information of the transmissionchannel of the multicast service data, or multicast-associated unicastconfiguration information.

In an optional implementation, the access network device furtherincludes:

an information receiving unit, configured to receive multicast serviceinformation sent by the user equipment or a core network device, wherethe multicast service information is used to instruct the user equipmentto receive the multicast service data, and the multicast serviceinformation includes identifier information of the user equipment andidentifier information of a multicast service.

In an optional implementation, that the information receiving unit isconfigured to receive multicast service information sent by the userequipment or a core network device includes:

receiving a multicast session establishment request sent by the corenetwork device, where the multicast session establishment requestincludes the identifier information of the user equipment and theidentifier information of the multicast service; or

receiving multicast member change information sent by the core networkdevice or the user equipment.

In an optional implementation, the access network device furtherincludes:

a manner determining unit, configured to: instruct, based on a quantityof user equipments that receive the multicast service data, the userequipment to receive the multicast service data in the unicast mannerand/or the multicast manner; or

receive channel measurement information sent by the user equipment, andinstruct, based on the channel measurement information, the userequipment to receive the multicast service data in the unicast mannerand/or the multicast manner.

In an optional implementation, the configuration information includesfirst multicast configuration information and second multicastconfiguration information; and

the indication information indicates that the manner of receiving themulticast service data includes the multicast manner, and the indicationinformation indicates that the first multicast configuration informationor the second multicast configuration information is used to receive themulticast service data.

In an optional implementation,

the data sending unit is further configured to send at least one datapacket in the multicast service data in the unicast manner as instructedby the user equipment; or

send at least one data packet in the multicast service data in theunicast manner as indicated by the core network device; or

send at least one data packet in the multicast service data in theunicast manner based on type information of the at least one datapacket.

In an optional implementation, the at least one data packet is multicastservice data that has been sent in the multicast manner and that isbuffered in the access network device, or multicast service data thathas been sent in the multicast manner and that is received from amulticast service data source.

In an optional implementation, the access network device furtherincludes:

a status receiving unit, configured to receive receiving statusinformation sent by the user equipment, where the receiving statusinformation is used to indicate a receiving status of the data packet inthe multicast service data, where

the data sending unit is further configured to send an unsuccessfullyreceived data packet in the multicast service data to the user equipmentin the unicast manner based on the receiving status information.

In an optional implementation, the data sending unit is configured to:send to-be-sent multicast service data to a unicast radio link controlRLC entity by using a packet data convergence protocol PDCP layer, andsend the to-be-sent multicast service data in the unicast manner.

In an optional implementation, the data sending unit is furtherconfigured to: replicate the to-be-sent multicast service data at thepacket data convergence protocol PDCP layer, and store the to-be-sentmulticast service data.

In an optional implementation, the data sending unit is configured to:send to-be-sent multicast service data to a multicast radio link controlRLC entity by using a multicast packet data convergence protocol PDCPlayer, where the multicast radio link control RLC entity sends theto-be-sent multicast service data to a unicast medium access control MACentity, and the unicast medium access control MAC entity sends theto-be-sent multicast service data in the unicast manner.

According to a fourth aspect, an embodiment of the present inventionfurther provides user equipment, including:

an indication receiving unit, configured to receive indicationinformation sent by an access network device, where the indicationinformation is used to indicate a manner of receiving multicast servicedata, and the receiving manner includes a unicast manner and/or amulticast manner; and

a data receiving unit, configured to receive the multicast service datain the unicast manner and/or the multicast manner indicated by theindication information.

In an optional implementation, the user equipment further includes:

a configuration receiving unit, configured to receive configurationinformation sent by the access network device, where the configurationinformation is used to receive the multicast service data.

In an optional implementation, the configuration information includes:

at least one of configuration information of a multicast bearer,multicast session information corresponding to the multicast bearer,logical channel information of the multicast bearer, multicastscheduling identifier information, information about a transmissionchannel for sending the multicast service data in the multicast manner,information about a transmission channel for sending the multicastservice data in the unicast manner, multicast logical channelinformation, measurement configuration information of the transmissionchannel of the multicast service data, or multicast-associated unicastconfiguration information.

In an optional implementation, the user equipment further includes:

an information sending unit, configured to send multicast serviceinformation to the access network device, where the multicast serviceinformation is used to instruct the user equipment to receive themulticast service data, and the multicast service information includesidentifier information of the user equipment and identifier informationof a multicast service.

In an optional implementation, that the information sending unit isconfigured to send multicast service information to the access networkdevice includes: sending multicast member change information to theaccess network device.

In an optional implementation,

the data receiving unit is configured to select, based on a quantity ofuser equipments that receive the multicast service data, the unicastmanner and/or the multicast manner for receiving the multicast servicedata; or

select, based on channel measurement information of the user equipment,the unicast manner and/or the multicast manner for receiving themulticast service data.

In an optional implementation, the configuration information includesfirst multicast configuration information and second multicastconfiguration information; and

the indication information indicates that the manner of receiving themulticast service data includes the multicast manner, and the indicationinformation indicates that the first multicast configuration informationor the second multicast configuration information is used to receive themulticast service data.

In an optional implementation, the user equipment further includes:

an indication sending unit, configured to instruct the access networkdevice to send at least one data packet in the multicast service data inthe unicast manner.

In an optional implementation, the user equipment further includes:

a status sending unit, configured to send receiving status informationto the access network device, where the receiving status information isused to indicate a receiving status of the data packet in the multicastservice data, where

the data receiving unit is configured to receive an unsuccessfullyreceived data packet in the multicast service data sent by the accessnetwork device.

In an optional implementation, the status sending unit is furtherconfigured to perform packet loss detection at a packet data convergenceprotocol PDCP layer to obtain the receiving status information.

In an optional implementation,

the data receiving unit is further configured to send, at a unicastradio link control RLC entity, the received multicast service data tothe multicast packet data convergence protocol PDCP layer.

According to a fifth aspect, an embodiment of the present inventionfurther provides an access network device, including a processor, amemory, and a transceiver, where the processor, the memory, and thetransceiver are connected in a manner supporting communication, where

the memory stores program code; and

the processor is configured to read the program code and cooperate withthe transceiver to implement the method that is performed by the accessnetwork device according to any one of the embodiments of the presentinvention.

According to a sixth aspect, an embodiment of the present inventionfurther provides user equipment, including a processor, a memory, and atransceiver, where the processor, the memory, and the transceiver areconnected in a manner supporting communication, where

the memory stores program code; and

the processor is configured to read the program code and cooperate withthe transceiver to implement the method that is performed by the userequipment according to any one of the embodiments of the presentinvention.

According to a seventh aspect, an embodiment of the present inventionfurther provides a storage medium, where the storage medium storesprogram code, the program code includes a program instruction, and whenthe program instruction is executed by a processor, the processor isenabled to cooperate with a transceiver to perform the method accordingto any one of the embodiments of the present invention.

According to an eighth aspect, an embodiment of the present inventionfurther provides a computer program product, where the computer programproduct includes a program instruction, and when the program code isexecuted by a processor, the processor is enabled to cooperate with atransceiver to perform the method according to any one of theembodiments of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention or in the background more clearly, the following brieflydescribes the accompanying drawings required for describing theembodiments of the present invention or the background.

FIG. 1A is a schematic diagram of a system architecture according to anembodiment of the present invention;

FIG. 1B is a schematic diagram of a system architecture according to anembodiment of the present invention;

FIG. 1C is a schematic diagram of a system architecture according to anembodiment of the present invention;

FIG. 2 is a schematic diagram of a system architecture according to anembodiment of the present invention;

FIG. 3 is a schematic flowchart of a method according to an embodimentof the present invention;

FIG. 4A is a schematic flowchart of a method according to an embodimentof the present invention;

FIG. 4B is a schematic flowchart of a method according to an embodimentof the present invention;

FIG. 4C is a schematic flowchart of a method according to an embodimentof the present invention;

FIG. 5 is a schematic diagram of user equipment distribution accordingto an embodiment of the present invention;

FIG. 6 is a schematic flowchart of a method according to an embodimentof the present invention;

FIG. 7 is a schematic diagram of user equipment distribution accordingto an embodiment of the present invention;

FIG. 8 is a schematic flowchart of a method according to an embodimentof the present invention;

FIG. 9 is a schematic flowchart of a method according to an embodimentof the present invention;

FIG. 10 is a schematic diagram of user equipment distribution accordingto an embodiment of the present invention;

FIG. 11 is a schematic diagram of a change in channel quality of userequipment according to an embodiment of the present invention;

FIG. 12 is a schematic flowchart of a method according to an embodimentof the present invention;

FIG. 13 is a schematic diagram in which a unicast manner and a multicastmanner are cooperated according to an embodiment of the presentinvention;

FIG. 14 is a schematic flowchart of a method according to an embodimentof the present invention;

FIG. 15 is a schematic diagram of a change in channel quality of userequipment according to an embodiment of the present invention;

FIG. 16 is a schematic diagram of a system in which a unicast manner anda multicast manner are cooperated according to an embodiment of thepresent invention;

FIG. 17 is a schematic structural diagram of a protocol stack accordingto an embodiment of the present invention;

FIG. 18A and FIG. 18B are a schematic structural diagram of a protocolstack according to an embodiment of the present invention;

FIG. 19 is a schematic structural diagram of a protocol stack accordingto an embodiment of the present invention;

FIG. 20 is a schematic structural diagram of an access network deviceaccording to an embodiment of the present invention;

FIG. 21 is a schematic structural diagram of user equipment according toan embodiment of the present invention;

FIG. 22 is a schematic structural diagram of a device according to anembodiment of the present invention; and

FIG. 23 is a schematic structural diagram of user equipment according toan embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following describes the embodiments of the present invention withreference to the accompanying drawings in the embodiments of the presentinvention. The term “and/or” describes an association relationshipbetween associated objects and indicates that three relationships mayexist. For example, A and/or B may indicate the following three cases:Only A exists, both A and B exist, and only B exists. The character “/”usually indicates an “or” relationship between the associated objects.“At least one of “A” or “B” means “A”, “B” or both “A” and “B”.

FIG. 1A to FIG. 1C each are a schematic structural diagram of acommunications system according to an embodiment of the presentinvention

The communications system in FIG. 1A includes user equipment, an accessnetwork device, a gateway device, a management device, a router, aserver, and the like. The management device and the gateway device maybe classified as core network devices, and the router and the server maybelong to a data network (DN).

In FIG. 1A, the user equipment may be connected, by using a wireless airinterface, to the access network device deployed by an operator, andthen connected to the data network. The access network device is mainlyconfigured to implement functions such as a radio physical layerfunction, resource scheduling and radio resource management, radioaccess control, and mobility management. The management device includedin the core network devices is mainly used for device registration,security authentication, mobility management, location management, andthe like of the user equipment. The gateway device in the core networkdevices is mainly configured to: establish a channel to the userequipment, and forward a data packet between the user equipment and anexternal data network on the channel. The data network is mainlyconfigured to provide a plurality of data services for the userequipment. The server included in the data network may be a fast channelchange (FCC) server. FIG. 1A is merely an example architectural diagram.In addition to the functional units shown in FIG. 1A, the networkarchitecture may further include another functional unit. This is notlimited in this embodiment of the present invention.

FIG. 1B and FIG. 1C are examples of FIG. 1A.

In the communications system shown in FIG. 1B, when a communicationsnetwork shown in FIG. 1A is a fifth generation (5G) network, the userequipment may be a mobile phone or a computer, or may be a cellularphone, a cordless phone, a session initiation protocol (SIP) phone, asmartphone, a wireless local loop (WLL) station, a personal digitalassistant (PDA), a computer, a laptop computer, a handheldcommunications device, a handheld computing device, a satellite wirelessdevice, a wireless modem card, a set top box (STB), a customer-premisesequipment (CPE), and/or another device used for communication in awireless system. The access network device may be an access network(AN)/radio access network (RAN) device, and the access network or theradio access network is a network including a plurality of 5G-AN/5G-RANnodes. The 5G-AN/5G-RAN node may be an access point (AP), anext-generation NodeB (NR nodeB, gNB), a transmission reception point(transmission receive point, TRP), a transmission point (TP), or anotheraccess node. The core network device may include functional units suchas an access and mobility management function (AMF), a sessionmanagement function (SMF), a policy control function (PCF), and a userplane function (UPF). These functional units may work independently, ormay be combined together to implement some control functions. Forexample, the AMF, the SMF, and the PCF may be combined together as amanagement device to implement access control and mobility managementfunctions such as access authentication, security encryption, andlocation registration of the user equipment, and session managementfunctions such as establishment, release, and change of a user planetransmission path, and functions of analyzing some data (such ascongestion) related to a slice and user equipment-related data. The UPFmainly completes functions such as routing and forwarding of user planedata, for example, is responsible for data packet filtering, datatransmission/forwarding, rate control, charging information generation,and the like for the user equipment.

FIG. 1B is a schematic diagram of a network architecture of a 5Gcommunications system. In a 5G network shown in FIG. 1B, functionalunits may communicate with each other by establishing a connectionbetween the functional units by using a next generation (NG) interface.For example, the user equipment may establish a control plane signalingconnection to the AMF by using an NG interface 1 (N1 for short). TheAN/RAN device, for example, a next-generation radio access NodeB (NRNodeB, gNB), may establish a user plane data connection to the UPF byusing an NG interface 3 (N3 for short), and the AN/RAN device mayestablish a control plane signaling connection to the AMF by using an NGinterface 2 (N2 for short). The UPF may establish a control planesignaling connection to the SMF by using an NG interface 4 (N4 forshort), and the UPF may exchange user plane data with the data networkby using an NG interface 6 (N6 for short). The AMF may establish acontrol plane signaling connection to the SMF by using an NG interface11 (N11 for short). The SMF may establish a control plane signalingconnection to the PCF by using an NG interface 7 (N7 for short). Itshould be noted that FIG. 1B is merely an example architectural diagram.In addition to the functional units shown in FIG. 1B, the networkarchitecture may further include another functional unit. For example,the core network device may further include a unified data management(unified data management, UDM) function. This is not limited in thisembodiment of the present invention.

When the communications network shown in FIG. 1A is a fourth generation(4G) network, for the user equipment, refer to related descriptions ofthe user equipment in FIG. 1B, and details are not described hereinagain. The access network device may be a NodeB (NB), an evolved NodeB(evolution nodeB, eNB), a TRP, a TP, an AP, or another access unit. Thecore network device may include a management device such as a mobilitymanagement entity (MME) or a policy and charging rules function, (PCRF),and a gateway device such as a serving gateway (SGW) or a PGW, and mayfurther include a local gateway (LGW).

For example, FIG. 1C is a schematic diagram of an architecture of a 4Gnetwork according to an embodiment of the present invention. In the 4Gnetwork shown in FIG. 1C, the user equipment may establish an airinterface connection to an eNB by using a Uu interface; the eNBestablishes a control plane signaling connection to the MME by using anS1-C interface, and the eNB establishes a user plane data connection tothe SGW by using an S1-U interface; and the SGW establishes a controlplane signaling connection to the MME by using an S11 interface, and theSGW establishes a user plane data connection to the PGW by using anS5/S8 interface. It should be noted that FIG. 1C is merely an examplearchitectural diagram. In addition to the functional units shown in FIG.1C, the network architecture may further include another functionalunit. This is not limited in this embodiment of the present invention.

To avoid loss of generality, FIG. 2 is a schematic diagram of acommunications system having a multicast architecture according to anembodiment of the present invention. A core network device includes acontrol plane network element and a user plane network element, whichare separately connected to an access network device. User equipment maybe connected to the access network device by using a wireless airinterface. The access network device is mainly configured to implementfunctions such as a radio physical layer function, resource schedulingand radio resource management, radio access control, and mobilitymanagement. The multicast core network device may include a multicastcore network control plane (CP), including multicast bearer management.The multicast core network device further includes a multicast corenetwork user plane (UP), configured to manage sending of multicast datafrom a multicast data network to the access network device. Themulticast core network user plane may correspond to an MBMS-GW in a 4Garchitecture, and the multicast core network control plane maycorrespond to an MME in the 4G architecture. It should be noted thatFIG. 2 is merely an example architectural diagram, and includes only aminimum quantity of network elements required by the multicast networkarchitecture. Therefore, in addition to the functional units shown inFIG. 2, the network architecture may further include another functionalunit.

FIG. 3 shows a process of establishing a multicast service bearer. Userequipment participating in multicast may be referred to as a multicastterminal. The user equipment, an access network device, a multicast corenetwork, and a multicast service platform first undergo a multicastservice discovery process. The multicast core network exchangesmulticast service information with the multicast service platform, andthe access network device exchanges multicast service information withthe multicast core network, so that a multicast service is established.The user equipment and the access network device determine a networkresource used for multicast, and then establish the radio bearer. Aspecific example is as follows.

The user equipment may find the multicast service platform in themulticast service discovery process. For example, the user equipment maybrowse an over the top (Over The Top, OTT) website and interact with aserver corresponding to the multicast service platform, to obtainmulticast data. Alternatively, the user equipment may find the multicastservice platform from a preconfigured address of the multicast serviceplatform. For example, a multicast service platform is usuallypre-configured in a set top box device. The user equipment interactswith the multicast service platform to obtain a multicast program listconfiguration. The multicast program list configuration includesmulticast address information, identifier information, or the like, andspecifically includes an internet protocol (internet protocol, IP)multicast address, an air interface multicast identifier, or the like. Auser selects a program in the user equipment, so that the user equipmentinteracts with the multicast service platform, the user equipment isadded as a receiver of the multicast service, and the user equipmentbecomes a participant of the multicast service. Compared with theforegoing process in which the user triggers the establishment of themulticast service, when the multicast service is in broadcast mode, themulticast service platform may also initiate a multicast serviceestablishment process with the multicast core network without triggeringof interaction between the multicast service platform and the userequipment. The multicast service may include a service such as groupcommunication of trunking communication or group forwarding of internetof vehicles. A manner of establishing the multicast service in theseapplication scenarios is similar to the foregoing OTT video or broadcastmanner.

Multicast session establishment: The multicast service platformexchanges information with the multicast core network, to triggerestablishment of a multicast session between the multicast core networkand the multicast access network device (for example, a base station).Alternatively, the core network may receive a message indicating thatthe user equipment joins the multicast service, to trigger establishmentof the multicast session. The multicast session may be carried by amulticast tunnel or may be identified by a multicast flow. In the formermanner, the multicast tunnel is established, the multicast data isplaced in the multicast tunnel and sent to the access network device,and multicast data of different multicast services (with differentmulticast addresses or different multicast QoS) are placed in differentmulticast tunnels. In the latter manner, a multicast flow identifier iscarried by a multicast packet, to distinguish between differentmulticast services. If the multicast session has been established beforethe user equipment joins the multicast service (for example, anotheruser equipment in a same access network has applied for joining themulticast service previously), the user equipment may directly join amulticast group to receive the multicast data.

In this embodiment of the present invention, to enable the accessnetwork device to flexibly adjust a manner of performing the multicastservice based on statuses of different user equipments, the accessnetwork device needs to learn of multicast service information of theuser equipment, and the multicast service information may include useridentifier information and a multicast service identifier. As shown inFIG. 4A, the multicast service information may be carried by a multicastsession establishment message during multicast session establishment.Alternatively, as shown in FIG. 4B, the multicast service informationmay be carried by a multicast join request or multicast member changeinformation. Alternatively, as shown in FIG. 4C, the multicast serviceinformation may be carried by multicast service receiving information.

FIG. 4A, FIG. 4B, and FIG. 4C show three different applicationscenarios, which are separately described below in detail.

FIG. 4A may show a scenario in which a multicast service is establishedfor the first time. A specific procedure may include the followingsteps.

401A: User equipment sends a multicast service join request to an accessnetwork device.

402A: The access network device forwards the received multicast servicejoin request to a multicast core network.

403A: The multicast core network sends a multicast session establishmentrequest to the access network device, where the multicast sessionestablishment request may carry multicast service information andmulticast configuration information.

The multicast service information may include user identifierinformation and a multicast service identifier. The multicastconfiguration information may include information about a resource thatneeds to be used by the multicast service.

404A: The access network device establishes a radio bearer based on themulticast configuration information. If a radio bearer has beenestablished between the access network device and the user equipment,and the radio bearer that has been established satisfies a requirementof a multicast configuration, this step may not be performed.

405A: The access network device sends a multicast session establishmentcomplete message to the multicast core network.

FIG. 4B may show a procedure of changing a multicast member after amulticast service is established. A specific procedure may include thefollowing steps.

401B: User equipment sends a multicast service join request to an accessnetwork device.

402B: The access network device forwards the received multicast servicejoin request to a multicast core network.

403B: The multicast core network finds that the multicast service to bejoined by the user equipment has been established, and sends multicastmember change information to the access network device, where themulticast member change information may carry user identifierinformation and a multicast service identifier.

403B may alternatively be: The multicast core network finds that themulticast service to be joined by the user equipment has beenestablished, and sends a multicast service join response to the accessnetwork device, where the multicast service join response may carry useridentifier information and a multicast service identifier.

404B: The access network device establishes a radio bearer based onmulticast configuration information corresponding to the multicastservice to be joined by the user equipment. If a radio bearer has beenestablished between the access network device and the user equipment,and the radio bearer that has been established satisfies a requirementof the multicast service, this step may not be performed.

In FIG. 4B, the user equipment sends the multicast service join request,and the multicast service join request may also carry the useridentifier information and the multicast service identifier, so that theaccess network device may also learn that the user equipment is to jointhe multicast service corresponding to the multicast service identifier.

In the foregoing procedure, for a process in which the user equipmentsends the multicast service join request to the access network device,and the access network device forwards the multicast service joinrequest, the multicast service join request may be sent by usingnon-access stratum signaling, and is transparently transmitted by theaccess network device. In FIG. 4B, the multicast member changeinformation may be dedicated indication information, and the dedicatedindication information may include identifier information of one or moremulticast member users.

FIG. 4C may show a procedure of changing a multicast member after amulticast service is established. A specific procedure may include thefollowing steps.

401C: User equipment sends multicast service receiving information to anaccess network device.

The multicast service receiving information may indicate a specificmulticast service that needs to be received by the user equipment. Aspecific manner may be that the multicast service receiving informationcarries a multicast service identifier. For example, the multicastservice identifier is a multicast IP address of the multicast service,or similar to a temporary mobile group identity (TMGI) of an MBMS.

402C: After receiving the multicast service receiving information, theaccess network device determines, based on the multicast serviceidentifier carried in the multicast service receiving information, aspecific multicast service group to which the user equipment joins. Theaccess network device may forward the multicast service receivinginformation to a multicast core network.

403C: The multicast core network may return a multicast service joinresponse, to notify the access network device that the user equipmenthas joined the multicast service.

In addition, in this embodiment of the present invention, for multicastinformation to be obtained by the access network device, the accessnetwork device may monitor a multicast join message of the userequipment, such as an internet group management protocol (IGMP) joinmessage sent by the user equipment, to obtain a correspondence betweenthe user equipment and the multicast service.

The access network device may select or adjust a multicast data sendingmanner based on statuses of different user equipments. The accessnetwork device may use an air interface wireless multicast manner, ormay use an air interface wireless unicast manner, or may use an airinterface wireless multicast and unicast cooperation manner. Thefollowing provides several common multicast service applicationscenarios.

1. Selection of a unicast manner or a multicast manner in a semi-staticmanner

As shown in FIG. 5, the unicast manner is used when there are a smallquantity of user equipments, and the multicast manner is used when thereare a large quantity of user equipments. A hexagonal area is an exampleof a cell. The hexagonal area may be one cell or a cell set including aplurality of cells. One black dot on the left side indicates one userequipment. Because there are a relatively small quantity of userequipments in a multicast group, to be specific, there are a relativelysmall quantity of user equipments participating in a multicast service,the unicast manner may be selected to be used. There are four userequipments in a multicast group on the right side, and the multicastmanner may be used. An example of a specific application scenario is asfollow:

(A)

In this embodiment, an example in which a unicast manner or a multicastmanner is selected in a semi-static manner is used. An access networkdevice determines, based on a quantity of user equipments of a multicastservice in a multicast area, to configure whether the user equipmentreceives multicast data in the unicast manner or the multicast manner.Correspondingly, the access network device sends multicast service datato the user equipment in the unicast manner or the multicast manner. Theaccess network device may alternatively configure that the userequipment may use the multicast manner and the unicast manner. Thisapplication scenario is described by using an example in the subsequentembodiments.

The multicast area may be one cell or more cells, or may similar to aplurality of single frequency network cells in an MBSFN.

The access network device may be a base station, or a centralized unit(CU) of a base station.

As shown in the left hexagonal area in FIG. 5, if there are a relativelysmall quantity of user equipments that receive the multicast servicedata, the access network device may configure the user equipment toreceive the multicast service data in the unicast manner. In this case,the user equipment may receive scheduling information of the basestation for a specific identity (identity, ID) of the user equipment,and perform corresponding data receiving and feedback. The specific IDmay be a cell radio network temporary identity (C-RNTI), a medium accesscontrol (MAC) address, or another ID that can uniquely identify the userequipment.

As shown in the right hexagonal area in FIG. 5, if a quantity of userequipments that receive the multicast service data in the multicast areais greater than a specified threshold, the base station may select tosend the multicast service data to the user equipment in the multicastgroup in the multicast manner, to save air interface resources. The basestation may configure the user equipment that receives the multicastservice data, so that all the user equipments can receive samescheduling information by using a same multicast ID, and receive samemulticast service data on a same radio resource. The multicast ID maybe, for example, a Group-RNIT, a group MAC address, a TMGI, or anothersimilar multicast service air interface ID. The specified threshold maybe preconfigured by an access network management system, or may becarried by a core network to an access network when a multicast sessionis established.

A specific procedure is shown in FIG. 6 and may include the followingsteps.

601: After a multicast session is established, the access network devicefinds that there are a small quantity of user equipments, so that theaccess network device establishes a radio bearer with user equipment 1,and sends multicast data in the unicast manner, and the user equipmentreceives the multicast data in the unicast manner.

In step 601, the user equipment 1 is configured to receive multicastservice data in the unicast manner. A configuration message may carryconfiguration information sent by the access network device to the userequipment. The configuration information may usually include one of thefollowing content: a configuration of a multicast bearer, multicastsession information corresponding to the multicast bearer, logicalchannel information of the multicast bearer, and indication informationtransmitted in the unicast manner. The multicast session information mayinclude evolved packet system (EPS) bearer information or EPS flowinformation.

More specifically, in step 601, after the multicast session isestablished, because the quantity of user equipments is too small, theaccess network device determines, based on the small quantity of userterminals that currently receive the multicast service data, thatsending efficiency is relatively high when the unicast manner is used,so that the user equipment 1 may be configured to receive the multicastservice data in the unicast manner. The configuration message may carrythe configuration information sent by the access network device to theuser equipment, and the configuration information may include at leastone of the following configuration information: bearer configurationinformation and resource layer configuration information.

The bearer configuration information may include at least one of thefollowing information: a radio bearer configuration and a securityconfiguration. The radio bearer configuration may carry one of thefollowing information: a radio bearer ID, an evolved packet systembearer ID corresponding to a multicast service, a quality of service(QoS) flow, configuration information of multicast service sessioninformation, PDCP configuration information, or RLC configurationinformation.

The multicast service session information may include a sessionidentifier (session ID), a TMGI identifier, and the like. The RLCconfiguration information may be a corresponding acknowledged mode (AM)RLC configuration or an unacknowledged mode (UM) RLC configuration, anda mapping relationship between the RLC configuration and a logicalchannel, to be specific, the RLC configuration may be mapped to aunicast logical channel or a multicast logical channel, or may be mappedto both a unicast logical channel and a multicast logical channel. TheRLC configuration may further include an AM or UM sending manner, andinformation about a logical channel to which the RLC configuration ismapped, for example, information indicating that the logical channel isa multicast logical channel or a unicast logical channel, or a logicalchannel ID. The PDCP configuration information may include a mappingrelationship between a PDCP layer and the RLC configuration (includingwhether the RLC configuration is mapped to only the unicast manner orthe multicast manner, or in a manner combining the unicast manner andthe multicast manner), and indication information indicating that thePDCP layer supports a retransmission function. The multicast logicalchannel includes a multicast control channel (multicast control channel,MCCH)/multicast traffic channel (multicast traffic channel, MTCH). Theunicast logical channel includes a dedicated control channel (dedicatecontrol channel, DCCH)/dedicated traffic channel (dedicated trafficchannel, DTCH).

The resource layer configuration information may include a MAC layerconfiguration and a physical layer configuration. The physical layerconfiguration may include a spectrum resource configuration, and may bein a form of one or more pieces of physical cell configurationinformation, carrier configuration information, or carrier fragmentconfiguration information, including a corresponding ID, a bandwidth, asubframe format, and the like. Further, the physical layer configurationmay further include physical video resource configuration information ofa corresponding physical channel/signal and corresponding identifierinformation, for example, configuration information of a unicastphysical control and shared channel and a unicast scheduling identifier,or configuration information of a multicast physical control and sharedchannel and a multicast scheduling identifier. The unicast physicalcontrol and shared channel and the multicast physical control and sharedchannel may be the same or share a same physical resource. The MAC layerconfiguration may include a mapping relationship between a unicast ormulticast logical channel and a corresponding physical channel, logicalchannel priority information, and HARQ configuration information.

The configuration message may further carry measurement information, forexample, measurement event configuration information used for switchingbetween the multicast manner and the unicast manner. The configurationmessage may further carry secure encryption/decryption information, forexample, an encryption/decryption algorithm for the multicast service.

602: New user equipment joins a multicast group.

603: A core network side may send a multicast session update message tothe access network device, to notify the access network device that thenew user equipment joins the multicast service.

604: The access network device finds that there are n user equipments inthe multicast group, and n reaches a threshold for specifying that theservice data is sent in the multicast manner. If the radio bearerestablished in the unicast manner is not applicable to the multicastmanner, the radio bearer between the access network device and the userequipment 1 may be updated.

605: The access network device establishes a radio bearer with the userequipment n, where the radio bearer is used to transmitting the data inthe multicast manner.

In the foregoing procedure, after receiving the information about theincrease in the quantity of user equipments of the same multicastservice, the access network device determines, according to a selectionalgorithm of the access network device, to select the multicast mannerfor sending the multicast service data, and the access network deviceconfigures the corresponding configuration information for thecorresponding user equipment, where the configuration informationcarries the corresponding multicast configuration.

In the foregoing procedure, the access network device in step 603 andstep 604 may learn of the quantity of user equipments in the multicastgroup. The foregoing selection algorithm may be: determining, if athreshold of a specified quantity of user equipments is reached, orbased on a channel status of the user equipment, that fewer radioresources are used to send the multicast service data in the multicastmanner than to send the multicast service data in the unicast mannerseparately, so that the access network device may determine to selectthe multicast manner for sending the multicast service data, andcorrespondingly, the user equipment receives the multicast service datain the multicast manner.

In the foregoing procedure, when the multicast radio bearer isestablished in step 604, the access network device may send themulticast configuration to the terminal, and the multicast configurationmay usually carry one of the following content: a configuration of amulticast bearer, multicast session information corresponding to themulticast bearer, logical channel information of the multicast bearer, amulticast scheduling identifier, a configuration of a multicasttransmission channel, a configuration of a multicast logical channel,measurement configuration of a multicast channel, multicast-associatedunicast configuration. A multicast session may include an EPS bearer oran EPS flow, the multicast scheduling identifier may include a groupradio network temporary identifier (group RNTI, G-RNTI, multicastidentifier for short), the configuration of the multicast transmissionchannel may include a subframe or a carrier, and the configuration ofthe multicast logical channel may include a logical channel identifier.

A difference between the manner of receiving the multicast service databy the user equipment in the unicast manner and the manner of receivingthe multicast service data by the user equipment in the multicast mannerlies in a difference in monitoring of physical layer schedulingidentifiers. If the user equipment receives the multicast service datain the unicast manner, the user equipment monitors and receives, basedon an identifier (such as a C-RNTI) of the user equipment, schedulingsignaling sent by a physical layer. If the user equipment receives themulticast service data in the multicast manner, the user equipmentmonitors and receives, based on a multicast identifier (such as aG-RNTI), scheduling signaling sent by a physical layer. Others, such asformats or sizes of control signaling for the unicast manner and themulticast manner may also be different. The control signaling may bedownlink control information (DCI). The user equipment may be in one ofa unicast manner receiving status or a multicast manner receivingstatus, so that an amount of signaling that needs to be monitored anddetected can be reduced. In addition, the user equipment mayalternatively be in both a unicast manner receiving status and amulticast manner receiving status. In this case, the user equipmentsimultaneously detects unicast scheduling signaling and multicastscheduling signaling that are sent by the access network device, andreceives the multicast service data on corresponding time-frequencyresources as indicated by the scheduling signaling.

(B)

FIG. 7 shows another application scenario of selecting a multicastmanner or a unicast manner. In user equipments that receive samemulticast service data, signal quality of some user equipments isrelatively poor due to reasons such as being located at an edge of acell. If all these user equipments are included in a multicast group,when sending the multicast service data in the multicast manner, anaccess network device needs to send the multicast data with relativelylow efficiency in consideration of user equipment with the worst signalquality. This causes a decrease in overall efficiency. In this case, theaccess network device may group the user equipments based on channelquality of the user equipments, and designate the user equipment withgood channel quality to receive the multicast service data in themulticast manner, and designate the user equipment with the poor channelquality to receive the multicast service data in the unicast manner.

A manner of obtaining the channel quality of the user equipment by theaccess network device may be that the access network device receives achannel measurement feedback sent by the user equipment, for example, ameasurement report or a channel state information (CSI) feedbackreported by the user equipment. The user equipment designated to receivethe multicast service data in the multicast manner may be user equipmentwhose channel quality is greater than a specified threshold. For theuser equipment whose channel quality is lower than the specifiedthreshold, the multicast manner for receiving the multicast service datamay be deleted or deactivated, to avoid the decrease in the overalltransmission efficiency of the multicast service data because the userequipments with the poor channel quality are enabled to successfullyreceive the data. For the user equipment with the relatively poorchannel quality, the access network device may send the multicastservice data in the unicast manner.

As shown in FIG. 8, a specific procedure may be as follows.

801: After a multicast session is established, an access network deviceestablishes a radio bearer with user equipment, where the radio bearerestablished for the first time may be applicable to establishment of amulticast service.

802: The user equipment sends a channel measurement feedback to theaccess network device.

803: The access network device finds, based on the channel measurementfeedback, that channel quality of the user equipment is relatively poor,which affects overall transmission efficiency of the multicast service,and establishes, with the user equipment, a radio bearer applicable to aunicast service.

In the foregoing procedure, for a radio bearer establishment process,refer to the foregoing embodiment, and details are not described hereinagain. In the foregoing procedure shown in FIG. 8, in the radio bearerestablishment process, only configuration information required by theradio bearer to be established may be sent. Specifically, in step 801,the access network device may send only multicast configurationinformation to the user equipment, and does not need to send unicastconfiguration information. In step 803, the access network device maysend only unicast configuration information, and does not need to sendmulticast configuration information. In addition, if the multicastservice is established for the first time, the user equipment may firstperform step 802, and then determine a type of a radio bearer to beestablished by the user equipment. In addition, for newly added userequipment, step 801 may not be performed. In the foregoing procedure,the multicast configuration information and the unicast configurationinformation may alternatively be sent in step 801, and subsequently, instep 803, the user equipment is instructed to only switch to the unicastmanner, or the user equipment determines that the channel quality ispoor and switches to the unicast manner.

FIG. 9 is an example of an implementation of another applicationscenario, including the following steps.

901: After a multicast session is established or a new multicast sessionis established, an access network device sends information such asmulticast configuration information, unicast configuration information,and a switching threshold to user equipment; and the user equipmentdetermines, based on the switching threshold, to establish a radiobearer with the access network device.

902: The user equipment may send a channel measurement report to theaccess network device, to notify the access network device of channelquality of the user equipment.

Because the user equipment already knows the switching threshold, theuser equipment may make a switching decision by itself. Another purposeof sending the measurement report may be to notify the access networkdevice that the user equipment has completed the switching.

In this embodiment, the access network device sends both the multicastconfiguration information and the unicast configuration information tothe user equipment, and may further send, to the user equipment, ameasurement threshold or a measurement event condition for receivingmulticast service data in a multicast manner or a unicast manner. Whenthe user equipment determines, through measurement and based on theswitching threshold, a condition for switching the receiving manner, theaccess network device is notified by using signaling, so that amulticast configuration or a unicast configuration is activated, acorresponding radio bearer is established, and then a correspondingreceiving manner is switched to. The signaling used to notify the accessnetwork device may be the channel measurement report.

(C)

As shown in FIG. 10, a multicast group may be divided into differentsub-multicast groups. In this embodiment, multicast service data mayfurther be grouped in a predetermined manner to improve overalltransmission efficiency. Because user equipments have differentdirections, an access network device may cover different user equipmentsthrough different beamforming. In addition, user equipments havingdifferent moving speeds may also be grouped into different sub-multicastgroups, and user equipments with different receiving capabilities mayalso be grouped into different groups. Different receiving capabilitiesmay be determined by, for example, a quantity of supported antennas,such as two antennas or four antennas.

In this embodiment, the access network device may obtain informationsuch as the receiving capability and a motion status of the userequipment by using a feedback channel of the user equipment, and reducea difference between users in a group as much as possible throughflexible grouping, thereby avoiding a decrease in multicast efficiency.To be specific, the multicast service data may be divided and sent by aplurality of sub-multicast groups, and may be sent by using an airinterface based on different multicast configurations. Multicast usersof different sub-multicast groups may be distinguished by configuringdifferent multicast scheduling identifiers or multicast transmissionchannel configurations, to avoid resource conflicts or interferencebetween the groups. The multicast scheduling identifier is, for example,a group RNTI; and the multicast transmission channel configuration is,for example, a subframe or a carrier.

In addition, the difference between the users in the group may also bereferred to as an intra-group difference, and is a difference betweenthe user equipments in the sub-multicast group. Because grouping is toimprove transmission efficiency of the multicast service data, areference value is usually a basis for grouping. The reference value maybe, for example, the motion status in the foregoing example. Userequipments with slow motions may be grouped into one group, and userequipments with fast motions may be grouped into one group.Alternatively, the reference value may be, for example, the direction ofthe user equipment. The user equipments may be grouped based on whetherantenna beamforming of the access network device can cover the userequipment and possible channel quality division after the coverage. Thisdifference is finally reflected by whether transmission efficiency ofthe sub-multicast group is reduced because impact exists between theuser equipments. Usually, the smaller a difference between referencevalues, the smaller the impact between the user equipments.

2. Dynamic selection of a unicast manner or a multicast manner in hybridmode

In the following example, user equipment participating in receivingmulticast service data may receive the multicast service data in boththe multicast manner and the unicast manner. The following examplefocuses on dynamic adjustment of the multicast manner and the unicastmanner.

(A)

As shown in FIG. 11, three curves A, B, and C respectively representchange statuses of channel quality in a period of time when three userequipments receive same multicast service data. In a time period t0 tot1, A, B, and C are in a phase in which the channel quality isrelatively good, and an access network device sends the data to A, B,and C in a multicast manner. In a time period t1 to t2, relativelystrong deterioration occurs in the channel quality of the user equipmentC. The channel quality deterioration may be caused by movement,temporary signal blocking, interference, or the like, and consequently,it cannot be ensured that the multicast service data is correctlyreceived. Receiving of the multicast service data in the unicast mannermay be adjusted through hybrid automatic retransmission (hybridautomatic repeat request, HARQ), dynamic scheduling, or adaptivemodulation and coding (AMC), to compensate for the deterioration of thechannel condition of the user equipment. Therefore, in the time periodt1 to t2, the user equipment A and the user equipment B may continue toreceive the multicast service data in the multicast manner, and the userequipment C may receive the multicast service data in the unicastmanner. After a moment t2, the channel quality of the user equipment Cis restored to a relatively good state, and the user equipment C mayreceive the multicast service data in the multicast manner again. Aspecific procedure may be shown in FIG. 12, and includes the followingsteps.

1201: Establish a radio bearer with user equipment after a multicastsession is established.

In this step, multicast configuration information and unicastconfiguration information may be sent at a time, and a multicast radiobearer or a unicast radio bearer may be selected for the radio bearer.Refer to the foregoing embodiment, and details are not described hereinagain.

1202: The user equipment sends a channel measurement feedback to anaccess network device.

Herein, the channel quality feedback carries information about channelquality of the user equipment, and may be specifically a measurementreport, a channel status report, or an uplink reference signal. Inaddition, in step 1201, a switching threshold may be specified in theconfiguration information. Therefore, if the user equipment determineswhether to switch a manner of receiving multicast service data, the userequipment may also send receiving manner switching indicationinformation in this step.

1203: The access network device may determine, based on the channelmeasurement feedback sent by the user equipment or the receiving mannerswitching indication information sent by the user equipment, that theuser equipment switches from receiving the multicast service data in amulticast manner to receiving the multicast service data in a unicastmanner, or switches from receiving the multicast service data in amulticast manner to receiving the multicast service data in a unicastmanner. The access network device sends a switching instruction to theuser equipment, and the user equipment switches the manner of receivingthe service data.

In FIG. 11, at a moment t1, the access network device determines thatthe user equipment C switches from receiving the multicast service datain the multicast manner to receiving the multicast service data in theunicast manner; and at the moment t2, the access network devicedetermines that the user equipment C switches from receiving themulticast service data in the unicast manner to receiving the multicastservice data in the multicast manner.

In this embodiment, the access network device may instruct, by usingsignaling, the user equipment C to switch from receiving the multicastservice data in the multicast manner to receiving the multicast servicedata in the unicast manner. In step 1203, the manner of receiving themulticast service data by the user equipment may be switched throughradio bearer reconfiguration. To perform switching more quickly, andmatch a fast channel status change, when the multicast service isestablished in step 1201, the access network device sends both themulticast configuration information and the unicast configurationinformation to the user equipment. When the manner needs to be switched,the access network device instructs, by using the switching instruction,the user equipment to switch the manner of receiving the multicastservice data, or activates a specified manner of receiving the multicastservice data. The switching instruction may be, for example, sent byusing a physical layer downlink control indicator (downlink controlindicator, DCI) or a MAC layer control element (control element, CE).

3. Multicast and unicast manner switching triggered by a service

In the following example, a manner of receiving multicast service databy user equipment may switch between a multicast manner and a unicastmanner. In the following example, the multicast service data needs to besent to the user equipment in the unicast manner, and subsequently, theuser equipment may receive the multicast service data in the multicastmanner.

FIG. 13 shows a scenario in which a service triggers switching of areceiving manner. Because in a multicast manner, sending and receivingare usually performed at a fixed rate, if user equipment has a specificrequirement, for example, needs to receive multicast service data at ahigher rate, the user equipment may interact with an access networkdevice by using signaling, and the access network device sends themulticast service data to the user equipment in a unicast manner. Asshown in the scenario marked in FIG. 12, the user equipment is receivinga video service. In a current common video encoding/decoding mannerH.264/H.265, image frames are organized by using a sequence as a unit,and there are an I-frame, a B-frame, and a P-frame, where the I-frame isa full-frame compressed coded frame, and a complete image can bereconstructed during decoding by using only data of the I-frame. TheB-frame and the P-frame are based on the I-frame and only a part that isdifferent from the I-frame is transmitted. In video information, thereis much of the same information between consecutive frames. Therefore,transmission of the same information can be reduced by using theB-frame/P-frame, thereby saving a transmission bandwidth. However, whenthe user equipment receives a new video, for example, clicks a newvideo, drags a progress bar, or switches a channel, an I-frame needs tobe decoded first to successfully play the new video. In a unicastservice, a server always sends data starting from an I-frame. However,in a multicast service, data is sent to a plurality of users at a sametime, a newly joined user cannot ensure that when the user joins themulticast service, the user can receive a new I-frame. As shown in FIG.13, the user equipment starts to receive the multicast service data at amoment T1, and at this moment, a previous I-frame has been sent, a nextI-frame is not sent, and the user equipment cannot correctly construct acomplete video frame based on a P-frame and a B-frame that are currentlyreceived. Therefore, the user equipment can be only in a black screenstate, and cannot immediately start to play a video. In this case, theuser equipment may instruct the access network device to send themulticast service data in the unicast manner, to send, at a relativelyhigh rate, an I-frame and the B-frame that are not received before, sothat the user equipment can immediately start to play the video. When adata frame received by the user equipment in the unicast manner isgreater than or equal to a sequence number of a current multicast dataframe, the user equipment may release a unicast resource, and switchback to the multicast manner to receive the multicast service data.

A core network device may distinguish between data packets of differenttypes by using tags in headers of the data packets, and the accessnetwork device may send the multicast service data based on indicationinformation of the core network device, and buffer the multicast servicedata for a time. When new user equipment joins a multicast group ororiginal user equipment starts to receive the multicast service data,the access network device may first send a segment of the multicastservice data in the unicast manner. The multicast service data may bebuffered by the access network device previously, and a sent start datapacket may be within a period of time or start from a latest specialtype of data packet. If the access network device does not buffer themulticast service data that needs to be sent in the unicast manner, themulticast service data sent in the unicast manner may be sent by thecore network device to the access network device. In a process ofestablishing or updating a multicast session, a unicast sending channelis established between the core network device and the access networkdevice, to send the multicast service data. After the multicast servicedata that needs to be sent in the unicast manner is sent, the accessnetwork device or the user equipment switches back to the multicastmanner to receive the multicast service data. In the foregoing scenarioin which the core network device sends the multicast service data to theaccess network device, a core network may notify an access network ofwhen to end sending of the multicast service data in the unicast manner,and separate signaling or a special identifier (for example, an endmarker of a GTP-U) in a data packet may be used to indicate that sendingof the multicast service data in the unicast manner ends. Similarly, theaccess network device may also instruct, by using dedicated signaling oran end data packet identifier, the user equipment to switch back to themulticast manner to receive the multicast service data. A video playingscenario is used as an example. For a specific process, refer to FIG.14. The process includes the following steps.

1401: After a multicast session is established, user equipment joins amulticast group, or user equipment switches to receive multicast servicedata in a multicast manner, and establishes a radio bearer applicable toreceiving the multicast service data in the multicast manner.

In this step, the user equipment may be user equipment that newly joinsthe multicast group, or may be existing user equipment in the multicastgroup.

1402: An access network device determines that a part of the multicastservice data needs to be sent to the user equipment in a unicast manner,and establishes a radio bearer with the user equipment, to send themulticast service data in the unicast manner.

A manner in which the access network device determines that themulticast service data needs to be sent to the user equipment in theunicast manner may include: specifying, by a core network device inprotocol headers of data packets, that some data packets, such as aB-frame and a P-frame, need to be sent in the unicast manner; or theaccess network device parses a received data packet, and if finding thatthe data packet is a B-frame or a P-frame, the access network devicedetermines that the data packet needs to be sent in the unicast manner.

1403: The access network device sends, to the user equipment, themulticast service data that needs to be sent in the unicast manner.

The multicast service data sent by the access network device in theunicast manner may be buffered by the access network device. Forexample, during a process of performing a multicast service, the accessnetwork device buffers a recently sent I-frame and data between theI-frame and a next I-frame that is not received, and uses the buffereddata as the multicast service data that needs to be sent in the unicastmanner. Alternatively, the multicast service data may be data obtainedfrom a source end of the multicast service. How to specifically obtainthe multicast service data that needs to be sent in the unicast manneris not uniquely described in this embodiment of the present invention.

1404: After sending the multicast service data that needs to be sent inthe unicast manner, the access network device switches the radio bearerbetween the access network device and the user equipment back to theradio bearer used to receive the multicast service data in the multicastmanner.

A switching manner may be sending, by the access network device, aswitching instruction to the user equipment, or may be reconfiguring theradio access bearer, to enable a newly established radio bearer to beadapted to send the service data in the multicast manner.

1405: The access network device sends the multicast service data to theuser equipment in the multicast manner.

4. Service continuity assurance during switching of a manner of sendingmulticast service data.

When the multicast manner is switched to the unicast manner, to ensurecontinuity of a multicast service, after switching to the unicastmanner, user equipment may notify, by using a data packet number, anaccess network device of a data packet that starts to be sent in theunicast manner. For example, the access network device may be notifiedof a sequence number of a last successfully received data packet, or asequence number of a next data packet that needs to be received; or theaccess network device may be notified by using a PDCP status report,where the PDCP status report is used to indicate that in data packetsfrom a sequence number N to a sequence number M, an identifier of a datapacket that is successfully received by the user equipment is 1, and anidentifier of a data packet that is not successfully received is 0.Based on information sent by the user equipment, the access networkdevice sends, in the unicast manner, a data packet that is not receivedby the user equipment, to ensure service continuity of the userequipment.

5. Cooperation between a unicast manner and a multicast manner in ahybrid sending manner:

The unicast manner and the multicast manner can be switched to eachother and can cooperate with each other. Currently, multicast servicedata is transmitted in the multicast manner without feedbackinformation, and cannot be retransmitted. Therefore, a multicast servicecan be transmitted only in a relatively conservative robust transmissionmanner, to ensure that a terminal can successfully receive the multicastservice data once in most scenarios. Because the conservativetransmission manner needs to sacrifice resource efficiency, in themulticast enhancement solution of this application, a feedback mechanismof user equipment participating in a multicast service may beintroduced. After the user equipment in a multicast group fails toreceive multicast service data, an access network device retransmits themulticast service data. In this embodiment of the present invention, themulticast service data may be retransmitted in the unicast manner.

As shown in FIG. 15 and FIG. 16, each of A, B, and C represents userequipment in a multicast group. Channel quality of the user equipment Cdeteriorates from T1 to T2, for example, the user equipment C enters acell edge or a channel is blocked, so that the user equipment C fails toreceive multicast service data. The user equipment C may notify, byusing feedback information, an access network device of a data packetthat needs to be retransmitted. In a process of retransmitting a datapacket, the user equipment may receive the multicast service data inboth a multicast manner and a unicast manner. With assistance of theunicast manner, reliability of the multicast manner can be higher, andthe multicast service data can be sent in a more efficient multicastmanner.

A manner in which the user equipment notifies the access network of thedata packet that needs to be retransmitted may be specifically asfollows.

The user equipment specifies, by using a fixed relationship betweenfeedback information and a retransmitted data packet, for example, amanner of sending a NACK by using a physical layer feedback channel,that the access network device retransmits, in the unicast manner, adata packet sent in an (n−k)^(th) subframe, where n is a subframe forsending the NACK. Alternatively, the user equipment may explicitlyindicate, by using an explicit data packet number, for example, an RLCor PDCP status report, that one or more data packets whose sequencenumbers are sequence number x (SNx) needs to be retransmitted.

In the foregoing embodiments, several typical scenarios and proceduresin which the multicast service is related to the air interfacetransmission are described by using examples. The following embodimentsfocus on describing user plane protocol stack structures of the accessnetwork device and the user equipment in a centralized manner.

FIG. 17, FIG. 18A and FIG. 18B show protocol stack structures forimplementing multicast and unicast cooperation at a PDCP layer,including a protocol stack structure on a transmit side of a multicastuser plane of an access network device and a protocol stack structure inwhich user equipment 1 to user equipment n are used as a receive side.For a service interface of an RLC layer, refer to multicast- andunicast-related protocol specifications, and details are not describedherein again.

The access network device establishes multicast bearers for differentmulticast sessions, and each multicast bearer corresponds to onemulticast PDCP layer. Mapping function entities from various services tothe bearer may be further added before the PDCP layer. For example, in5G, there is an SDAP (service data adaptation protocol, service dataadaptation protocol) layer above the PDCP layer, and the SDAP layer isused for mapping from a flow (flow) to the PDCP layer, and is irrelevantto a function of core content in this embodiment of the presentinvention, so that descriptions are omitted subsequently. The multicastPDCP adds a sequence number (sequence number, SN) to the multicastservice SDU, and the SN is used by a receive side for data packetsorting and retransmission requests. The multicast PDCP layer canfurther encrypt a multicast data packet. The multicast PDCP layer uses aservice encryption key instead of a terminal encryption key, to ensurethat different users can decrypt the multicast PDCP layer. The PDCPlayer may also perform header compression on a header of the datapacket. Then, a PDCP header is added to the data packet, and the datapacket with the PDCP header is sent to a replication and routing module.A data packet sent in the unicast manner at a bottom layer can bereplicated and then buffered to a queue for processing a subsequentretransmission request. A data packet sent in the multicast manner maynot need to be replicated and buffered.

After processing the data packet, the PDCP layer sends obtained packetdata unit (packet data unit, PDU) data to an RLC module. Becausefeedback cannot be performed in the multicast manner, a multicast RLCentity may further map the data to a multicast MAC entity at the bottomlayer by using a UM mode, and send, by using an independent HARQ entityand an independent scheduling identifier (such as a G-RNTI), the data ona multicast physical channel provided by a corresponding multicastphysical layer. For user equipment in a unicast state, the multicastPDCP layer may send, based on member information of a multicast group,the data to a unicast RLC entity that is associated with a multicastservice and that is of the corresponding user equipment. Herein, the RLCentity may select an AM mode or the UM mode, and then the RLC entity ofthe user equipment sends the data to a unicast MAC entity. The unicastHARQ entity of the user equipment is responsible for unicast scheduling,and sending HARQ data at a unicast physical layer.

It can be learned from the foregoing scenario descriptions that the userequipment may use the unicast manner or the multicast manner, or may usea hybrid mode in which both the unicast manner and the multicast mannerwork. When only one receiving or sending manner is used, the userequipment may receive the data packet by using the multicast RLC entityor the unicast RLC entity based on a configuration of the access networkdevice, and then deliver the data packet to the multicast PDCP layer. Inthe hybrid mode, the multicast RLC entity and the unicast RLC entity maysimultaneously submit the PDU data to the multicast PDCP layer, and thePDCP layer sorts or repeatedly determines, based on the SN, the PDU datasubmitted by the RLC entity. When the PDCP layer determines that a datapacket is lost, for example, when SNs are nonconsecutive, the PDCP layermay initiate a retransmission request, for example, notify the accessnetwork device of a missing data packet SN number by using a PDCP statusreport. The retransmission request is fed back to a unicast RLC entitycorresponding to the access network device in the unicast manner, and issubmitted by the unicast RLC entity of the access network device to themulticast PDCP layer. The multicast PDCP layer retransmits the PDU datawith the corresponding SN by using the unicast RLC entity. In this way,data retransmission is complete.

FIG. 19 shows a protocol stack structure in which a multicast manner anda unicast manner are switched at an RLC layer. A multicast RLC entity isresponsible for segmenting a data packet, and then sends the data packetto a multicast MAC entity for sending. For user equipment that uses theunicast manner, the multicast RLC entity replicates PDU data and sendsthe PDU data to a unicast MAC HARQ entity corresponding to the userequipment for unicast sending. When the user equipment is in a hybridmode and receiving in the multicast manner fails, an automatic repeatrequest (ARQ) entity of the user equipment initiates an RLC statusreport, to request a multicast RLC entity of an access network device toretransmit PDU data corresponding to a missing RLC SN identifier.Compared with the method in which the switching is controlled by thePDCP layer, retransmission initiated by the multicast RLC entity may beperformed at an RLC PDU granularity, thereby avoiding retransmission ofentire PDCP PDU data. The entire PDCP PDU data is usually retransmittedat an IP packet granularity, and the multicast RLC entity may segmentthe multicast PDCP PDU data into several segments based on a resourcestatus of an air interface, so that a problem of a waste ofretransmission resources caused by a large retransmission granularity isavoided. When the user equipment requests to retransmit data, themulticast RLC entity may further segment, based on a current radioresource status of the user equipment, the RLC PDU data again that needsto be retransmitted.

The embodiments of the present invention may be applied to various radioaccess standards, and cooperation between the multicast manner and theunicast manner is implemented based on the PDCP layer, so that, forexample, LTE multicast, NR unicast, LTE multicast, or WLAN unicast isimplemented.

An embodiment of the present invention further provides an accessnetwork device. As shown in FIG. 20, the access network device includes:

an indication sending unit 2001, configured to send indicationinformation to user equipment, where the indication information is usedto indicate a manner of receiving multicast service data, and thereceiving manner includes a unicast manner and/or a multicast manner;and

a data sending unit 2002, configured to send the multicast service datain the unicast manner and/or the multicast manner indicated by theindication information.

In an optional implementation, the access network device furtherincludes:

a configuration sending unit 2003, configured to send configurationinformation to the user equipment, where the configuration informationis used to receive the multicast service data.

In an optional implementation, the configuration information includes:

at least one of configuration information of a multicast bearer,multicast session information corresponding to the multicast bearer,logical channel information of the multicast bearer, multicastscheduling identifier information, information about a transmissionchannel for sending the multicast service data in the multicast manner,information about a transmission channel for sending the multicastservice data in the unicast manner, multicast logical channelinformation, measurement configuration information of the transmissionchannel of the multicast service data, and multicast-associated unicastconfiguration information.

In an optional implementation, the access network device furtherincludes:

an information receiving unit 2004, configured to receive multicastservice information sent by the user equipment or a core network device,where the multicast service information is used to instruct the userequipment to receive the multicast service data, and the multicastservice information includes identifier information of the userequipment and identifier information of a multicast service.

In an optional implementation, that the information receiving unit 2004is configured to receive multicast service information sent by the userequipment or a core network device includes:

receiving a multicast session establishment request sent by the corenetwork device, where the multicast session establishment requestincludes the identifier information of the user equipment and theidentifier information of the multicast service; or

receiving multicast member change information sent by the core networkdevice or the user equipment.

In an optional implementation, the access network device furtherincludes:

a manner determining unit 2005, configured to: instruct, based on aquantity of user equipments that receive the multicast service data, theuser equipment to receive the multicast service data in the unicastmanner and/or the multicast manner; or

receive channel measurement information sent by the user equipment, andinstruct, based on the channel measurement information, the userequipment to receive the multicast service data in the unicast mannerand/or the multicast manner.

In an optional implementation, the configuration information includesfirst multicast configuration information and second multicastconfiguration information; and

the indication information indicates that the manner of receiving themulticast service data includes the multicast manner, and the indicationinformation indicates that the first multicast configuration informationor the second multicast configuration information is used to receive themulticast service data.

In an optional implementation,

the data sending unit 2002 is further configured to: send at least onedata packet in the multicast service data in the unicast manneraccording to as instructed by the user equipment; or

send at least one data packet in the multicast service data in theunicast manner as indicated by the core network device; or

send at least one data packet in the multicast service data in theunicast manner based on type information of the at least one datapacket.

In an optional implementation, the at least one data packet is multicastservice data that has been sent in the multicast manner and that isbuffered in the access network device, or multicast service data thathas been sent in the multicast manner and that is received from amulticast service data source.

In an optional implementation, the access network device furtherincludes:

a status receiving unit 2006, configured to receive receiving statusinformation sent by the user equipment, where the receiving statusinformation is used to indicate a receiving status of the data packet inthe multicast service data, where

the data sending unit 2002 is further configured to send anunsuccessfully received data packet in the multicast service data to theuser equipment in the unicast manner based on the receiving statusinformation.

In an optional implementation, the data sending unit 2002 is configuredto: send to-be-sent multicast service data to a unicast radio linkcontrol RLC entity by using a packet data convergence protocol PDCPlayer, and send the to-be-sent multicast service data in the unicastmanner.

In an optional implementation, the data sending unit 2002 is furtherconfigured to: replicate the to-be-sent multicast service data at thepacket data convergence protocol PDCP layer, and store the to-be-sentmulticast service data.

In an optional implementation, the data sending unit 2002 is configuredto: send to-be-sent multicast service data to a multicast radio linkcontrol RLC entity by using a multicast packet data convergence protocolPDCP layer, where the multicast radio link control RLC entity sends theto-be-sent multicast service data to a unicast medium access control MACentity, and the unicast medium access control MAC entity sends theto-be-sent multicast service data in the unicast manner.

An embodiment of the present invention further provides user equipment.As shown in FIG. 21, the user equipment includes:

an indication receiving unit 2101, configured to receive indicationinformation sent by an access network device, where the indicationinformation is used to indicate a manner of receiving multicast servicedata, and the receiving manner includes a unicast manner and/or amulticast manner; and

a data receiving unit 2102, configured to receive the multicast servicedata in the unicast manner and/or the multicast manner indicated by theindication information.

In an optional implementation, the user equipment further includes:

a configuration receiving unit 2103, configured to receive configurationinformation sent by the access network device, where the configurationinformation is used to receive the multicast service data.

In an optional implementation, the configuration information includes:

at least one of configuration information of a multicast bearer,multicast session information corresponding to the multicast bearer,logical channel information of the multicast bearer, multicastscheduling identifier information, information about a transmissionchannel for sending the multicast service data in the multicast manner,information about a transmission channel for sending the multicastservice data in the unicast manner, multicast logical channelinformation, measurement configuration information of the transmissionchannel of the multicast service data, and multicast-associated unicastconfiguration information.

In an optional implementation, the user equipment further includes:

an information sending unit 2104, configured to send multicast serviceinformation to the access network device, where the multicast serviceinformation is used to instruct the user equipment to receive themulticast service data, and the multicast service information includesidentifier information of the user equipment and identifier informationof a multicast service.

In an optional implementation, that the information sending unit 2104 isconfigured to send multicast service information to the access networkdevice includes: sending multicast member change information to theaccess network device.

In an optional implementation,

the data receiving unit 2102 is configured to: select, based on aquantity of user equipments that receive the multicast service data, theunicast manner and/or the multicast manner for receiving the multicastservice data; or

select, based on channel measurement information of the user equipment,the unicast manner and/or the multicast manner for receiving themulticast service data.

In an optional implementation, the configuration information includesfirst multicast configuration information and second multicastconfiguration information; and

the indication information indicates that the manner of receiving themulticast service data includes the multicast manner, and the indicationinformation indicates that the first multicast configuration informationor the second multicast configuration information is used to receive themulticast service data.

In an optional implementation, the user equipment further includes:

an indication sending unit 2105, configured to instruct the accessnetwork device to send at least one data packet in the multicast servicedata in the unicast manner.

In an optional implementation, the user equipment further includes:

a status sending unit 2106, configured to send receiving statusinformation to the access network device, where the receiving statusinformation is used to indicate a receiving status of the data packet inthe multicast service data, where

the data receiving unit 2102 is configured to receive an unsuccessfullyreceived data packet in the multicast service data sent by the accessnetwork device.

In an optional implementation, the status sending unit 2106 is furtherconfigured to perform packet loss detection at a packet data convergenceprotocol PDCP layer to obtain the receiving status information.

In an optional implementation,

the data receiving unit 2102 is further configured to send, at a unicastradio link control RLC entity, the received multicast service data tothe multicast packet data convergence protocol PDCP layer.

FIG. 22 shows a device 220 according to an embodiment of the presentinvention. The device 220 includes a processor 2201, a memory 2202, anda transceiver 2203. The processor 2201, the memory 2202, and thetransceiver 2203 are connected to each other by using a bus.

The memory 2202 includes but is not limited to a random access memory(random access memory, RAM), a read-only memory (read-only memory, ROM),an erasable programmable read-only memory (erasable programmable readonly memory, EPROM), or a compact disc read-only memory (compact discread-only memory, CD-ROM). The memory 2202 is configured to store arelated instruction and related data. The transceiver 2203 is configuredto receive and send data.

The processor 2201 may be one or more central processing units (centralprocessing unit, CPU). When the processor 2201 is one CPU, the CPU maybe a single-core CPU or a multi-core CPU.

The processor 2201 in the device 220 is configured to read program codestored in the memory 2202,

The memory 2202 stores program code.

The processor 2201 is configured to read the program code, and cooperatewith the transceiver 2203 to implement any method performed by theaccess network device or the user equipment according to any one of theembodiments of the present invention. The transceiver 2203 may implementfunctions of various units that implement reception and transmissionfunctions in the foregoing user equipment or the access network device,and another function is implemented by the processor 2201.

FIG. 23 shows user equipment 230 according to some embodiments of thisapplication. As shown in FIG. 23, the user equipment 230 may includeinput/output modules (including an audio input/output module 2318, a keyinput module 2316, a display 2320, and the like), a user interface 2302,one or more processors 2304, a transmitter 2306, a receiver 2308, acoupler 2310, an antenna 2314, and a memory 2312. These components maybe connected by using a bus or in another manner. In FIG. 23, an examplein which the components are connected by using a bus is used.

The antenna 2314 may be configured to convert electromagnetic energyinto an electromagnetic wave in free space, or convert anelectromagnetic wave in free space into electromagnetic energy in atransmission line. The coupler 2310 is configured to divide a mobilecommunications signal received by the antenna 2314 into a plurality ofsignals, and allocate the plurality of signals to a plurality ofreceivers 2308.

The transmitter 2306 may be configured to transmit a signal output bythe processor 2304.

The receiver 2308 may be configured to receive a mobile communicationssignal received by the antenna 2314.

In some embodiments of this application, the transmitter 2306 and thereceiver 2308 may be considered as a wireless modem. In the userequipment 230, there may be one or more transmitters 2306 and one ormore receivers 2308.

In addition to the transmitter 2306 and the receiver 2308 shown in FIG.23, the user equipment 230 may further include other communicationscomponents, for example, a GPS module, a Bluetooth (Bluetooth) module,and a wireless fidelity (wireless fidelity, Wi-Fi) module. In additionto the foregoing described wireless communications signal, the userequipment 230 may support another wireless communications signal, forexample, a satellite signal or a short wave signal.

The input/output modules may be configured to implement interactionbetween the user equipment 230 and a user/an external environment, andmay mainly include the audio input and output module 2318, the key inputmodule 2316, the display 2320, and the like. Specifically, theinput/output modules may further include a camera, a touchscreen, asensor, and the like. All the input/output modules communicate with theprocessor 2304 by using the user interface 2302.

The memory 2312 is coupled to the processor 2304, and is configured tostore various software programs and/or a plurality of sets ofinstructions. Specifically, the memory 2312 may include a high-speedrandom access memory, and may include a non-volatile memory, forexample, one or more magnetic disk storage devices, a flash memorydevice, or another non-volatile solid-state storage device. The memory2312 may store an operating system (briefly referred to as a systembelow), for example, an embedded operating system such as Android, iOS,Windows, or Linux. The memory 2312 may further store a networkcommunications program. The network communications program may beconfigured to communicate with one or more additional devices, one ormore user equipments, or one or more network devices. The memory 2312may further store a user interface program. The user interface programmay vividly display content of an application program by using agraphical operation interface, and receive control operations of a userfor the application program by using input controls such as a menu, adialog box, and a key.

In some embodiments of this application, the memory 2312 may beconfigured to store a program for implementing, on a side of the userequipment 230, the system message receiving method according to one ormore embodiments of this application. For implementation of the systemmessage receiving method according to one or more embodiments of thisapplication, refer to subsequent embodiments.

The processor 2304 may be configured to read and execute acomputer-readable instruction. Specifically, the processor 2304 may beconfigured to: invoke a program stored in the memory 2312, and executean instruction included in the program, to implement the method insubsequent embodiments.

It may be understood that the user equipment 230 may be user equipmentin the communications system described above in the embodiments of thepresent invention, and may be implemented as a mobile device, a mobilestation, a mobile unit, a radio unit, a remote unit, a user agent, amobile client, or the like.

It should be noted that the user equipment 230 shown in FIG. 23 ismerely an implementation of the embodiments of this application. In anactual application, the user equipment 230 may include more or fewercomponents, and this is not limited herein. In this embodiment, theprocessor 23 may correspond to the processor shown in FIG. 22. Thetransmitter 2306 and the receiver 2308 may respectively correspond tounits for implementing a transmission function and a reception function.

An embodiment of the present invention further provides a storagemedium. The storage medium stores program code, and the program codeincludes a program instruction. When the program instruction is executedby a processor, the processor cooperates with a transceiver to performthe foregoing method according to any one of the embodiments of thepresent invention.

An embodiment of the present invention further provides a computerprogram product. The computer program product includes a programinstruction. When the program code is executed by a processor, theprocessor cooperates with a transceiver to perform the foregoing methodaccording to any one of the embodiments of the present invention.

A person of ordinary skill in the art may understand that all or some ofthe procedures of the methods in the embodiments may be implemented by acomputer program instructing relevant hardware. The program may bestored in a computer-readable storage medium. When the program is run,the foregoing method procedures are performed. The foregoing storagemedium includes: any medium that can store program code, such as a readonly memory (ROM) or a random access memory (RAM), a magnetic disk, oran optical disc.

What is claimed is:
 1. A method, comprising: sending, by an accessnetwork device, configuration information comprising first multicastconfiguration information and second multicast configuration informationto user equipment, wherein the configuration information is used toreceive multicast service data; sending, by the access network device,indication information indicating that a multicast manner of receivingthe multicast server data is to be used to the user equipment, theindication information also indicating whether the first multicastconfiguration information or the second multicast configurationinformation is to be used to receive the multicast service data; and,sending, by the access network device, the multicast service data in themulticast manner as indicated by the indication information.
 2. Themethod according to claim 1, wherein the configuration informationcomprises: at least one of configuration information of a multicastbearer, multicast session information corresponding to the multicastbearer, logical channel information of the multicast bearer, multicastscheduling identifier information, information about a transmissionchannel for sending the multicast service data in the unicast manner,multicast logical channel information, measurement configurationinformation of the transmission channel of the multicast service data,and multicast-associated unicast configuration information.
 3. Themethod according to claim 1, further comprising: receiving, by theaccess network device, multicast service information sent by the userequipment or a core network device, wherein the multicast serviceinformation is used to instruct the user equipment to receive themulticast service data, and the multicast service information comprisesidentifier information of the user equipment and identifier informationof a multicast service.
 4. The method according to claim 3, wherein thereceiving, by the access network device, multicast service informationsent by the user equipment or the core network device comprises:receiving, by the access network device, a multicast sessionestablishment request sent by the core network device, wherein themulticast session establishment request comprises the identifierinformation of the user equipment and the identifier information of themulticast service; or receiving, by the access network device, multicastmember change information sent by the core network device or the userequipment.
 5. The method according to claim 1, further comprising:Instructing, by the access network device based on a quantity of userequipments that receive the multicast service data, the user equipmentto receive the multicast service data in the unicast manner; orreceiving, by the access network device, channel measurement informationsent by the user equipment, and instructing, based on the channelmeasurement information, the user equipment to receive the multicastservice data in the unicast manner.
 6. The method according to claim 1,further comprising: sending, by the access network device, at least onedata packet in the multicast service data in the unicast manner asinstructed by the user equipment; or sending, by the access networkdevice, at least one data packet in the multicast service data in theunicast manner as indicated by a core network device; or sending, by theaccess network device, at least one data packet in the multicast servicedata in the unicast manner based on type information of the at least onedata packet.
 7. The method according to claim 1, wherein the userequipment processes the indication information to indicate the multicastmanner is to be used to receive the multicast service data by evaluatingthe configuration information to see if the configuration informationincludes unicast configuration information, and if not, uses themulticast manner to receive the multicast service data.
 8. A device,comprising: a processor; a memory; and a transceiver; wherein: theprocessor, the memory, and the transceiver are connected in a mannersupporting communication; the memory stores program code; and theprocessor is configured to read the program code and cooperate with thetransceiver to: send indication information to user equipment, whereinthe indication information is used to indicate a manner of receivingmulticast service data, and the receiving manner comprises a unicastmanner and/or a multicast manner, and the indication informationindicates that the manner of receiving the multicast service datacomprises the multicast manner; send configuration information to theuser equipment, wherein the configuration information comprises firstmulticast configuration information and second multicast configurationinformation, and the indication information indicates that the firstmulticast configuration information or the second multicastconfiguration information is used to receive the multicast service data,and is used to receive the multicast service data; and send themulticast service data in the unicast manner and/or the multicast mannerindicated by the indication information.
 9. The device according toclaim 8, wherein the configuration information comprises: at least oneof configuration information of a multicast bearer, multicast sessioninformation corresponding to the multicast bearer, logical channelinformation of the multicast bearer, multicast scheduling identifierinformation, information about a transmission channel for sending themulticast service data in the multicast manner, information about atransmission channel for sending the multicast service data in theunicast manner, multicast logical channel information, measurementconfiguration information of the transmission channel of the multicastservice data, or multicast-associated unicast configuration information.10. The device according to claim 8, wherein the processor is configuredto read the program code and cooperate with the transceiver to: Receivemulticast service information sent by the user equipment or a corenetwork device, wherein the multicast service information is used toinstruct the user equipment to receive the multicast service data, andthe multicast service information comprises identifier information ofthe user equipment and identifier information of a multicast service.11. The device according to claim 10, wherein the receiving multicastservice information sent by the user equipment or the core networkdevice comprises: receiving a multicast session establishment requestsent by the core network device, wherein the multicast sessionestablishment request comprises the identifier information of the userequipment and the identifier information of the multicast service; orreceiving multicast member change information sent by the core networkdevice or the user equipment.
 12. The device according to claim 8,wherein the processor is configured to read the program code andcooperate with the transceiver to: instruct, based on a quantity of userequipments that receive the multicast service data, the user equipmentto receive the multicast service data in the unicast manner and/or themulticast manner; or receive channel measurement information sent by theuser equipment, and instructing, based on the channel measurementinformation, the user equipment to receive the multicast service data inthe unicast manner and/or the multicast manner.
 13. The access networkdevice according to claim 8, wherein the processor is configured to readthe program code and cooperate with the transceiver to implement thestep of: sending at least one data packet in the multicast service datain the unicast manner as instructed by the user equipment; or sending atleast one data packet in the multicast service data in the unicastmanner as indicated by a core network device; or sending at least onedata packet in the multicast service data in the unicast manner based ontype information of the at least one data packet.
 14. The deviceaccording to claim 8, wherein the processor is further configured toread the program code and cooperate with the transceiver to: configurethe indication information to indicate the multicast manner is to beused to receive the multicast service data by not including unicastconfiguration information in the configuration information, and thuscausing the user equipment to use the multicast manner to receive themulticast service data.
 15. A non-transitory storage medium, wherein thestorage medium stores program code, the program code comprises a programinstruction, and when the program instruction is executed by aprocessor, the processor is enabled to cooperate with a transceiver to:send indication information to user equipment, wherein the indicationinformation is used to indicate a manner of receiving multicast servicedata, and the receiving manner comprises a unicast manner and/or amulticast manner, and the indication information indicates that themanner of receiving the multicast service data comprises the multicastmanner; send configuration information to the user equipment, whereinthe configuration information comprises first multicast configurationinformation and second multicast configuration information, and theindication information indicates that the first multicast configurationinformation or the second multicast configuration information is used toreceive the multicast service data, and is used to receive the multicastservice data; and send the multicast service data in the unicast mannerand/or the multicast manner indicated by the indication information. 16.The non-transitory storage medium according to claim 15, wherein theprocessor is further configured to read the program code and cooperatewith the transceiver to: configure the indication information toindicate the multicast manner is to be used to receive the multicastservice data by not including unicast configuration information in theconfiguration information, and thus causing the user equipment to usethe multicast manner to receive the multicast service data.
 17. Thenon-transitory storage medium according to claim 15, wherein theprocessor is further configured to read the program code and cooperatewith the transceiver to: send the multicast service data to a unicastradio link control (RLC) entity by using a packet data convergenceprotocol (PDCP) layer, and sending the multicast service data in theunicast manner; or send the multicast service data to a multicast RLCentity by using a multicast PDCP layer; sending, by the multicast RLCentity, the multicast service data to a unicast medium access control(MAC) entity; and sending, by the unicast MAC entity, the multicastservice data in the unicast manner.